A method for preparing and applying a transparent superhydrophobic coating

Abstract

This invention belongs to the field of hydrophobic coatings, and particularly relates to a method for preparing and applying a transparent superhydrophobic coating. The preparation method includes the following steps: blending polyvinylidene fluoride-trifluoroethylene copolymer, PDMS, and a solvent to obtain a spinning solution; and forming a superhydrophobic transparent coating on a substrate surface by electrospinning. The mass ratio of polyvinylidene fluoride-trifluoroethylene copolymer to PDMS is 1:0 to 1:10, and the concentrations of polyvinylidene fluoride-trifluoroethylene copolymer and PDMS in the spinning solution are 5 to 30 wt%. This invention pre-forms an accelerator layer and a crosslinking agent layer on the substrate. The crosslinking agent layer increases the bonding strength between the accelerator layer and the substrate, and crosslinks with the polyvinylidene fluoride-trifluoroethylene copolymer and PDMS in the electrospinning solution. The superhydrophobic coating formed by electrospinning has an inter-crosslinked nanofiber structure, and the fibers inter-crosslink to form a network structure with numerous pores, thus forming a superhydrophobic coating that combines superhydrophobicity and optical transparency.

Description

Technical Field

[0001] This invention belongs to the field of hydrophobic coatings, and particularly relates to a method for preparing and applying a transparent superhydrophobic coating. Background Technology

[0002] Variations in ambient temperature and humidity can lead to the accumulation of water droplets, fog, and frost, significantly reducing the transparency of optical glass and impacting its applications in automotive windshields, architectural windows, and camera lenses. To address this issue, researchers have developed various functional coatings designed to repel or attract water, including superhydrophobic and superhydrophilic coatings. These coatings have all proven effective in mitigating the negative effects of moisture accumulation.

[0003] However, compared to superhydrophilic coatings, lotus leaf-inspired superhydrophobic coatings allow water droplets to roll off, achieving a self-cleaning function. Furthermore, the micro / nanostructure of superhydrophobic coatings contains air pockets that can slow the freezing process by hindering heat transfer and reducing the contact area between the liquid and the surface, thus preventing the accumulation of fog and frost. Superhydrophobic surfaces have been developed to integrate anti-icing, anti-frost, and self-healing functions. However, achieving a balance between surface roughness, transparency, and durability remains challenging.

[0004] Methods for constructing superhydrophobic coatings include chemical vapor deposition, etching, template-based processes, self-assembly, and sol-gel processes. The resulting superhydrophobic coatings typically exhibit non-uniform and uncontrollable surface morphologies. This leads to light scattering on the superhydrophobic coating surface, thus adversely affecting the transparency of optical glass.

[0005] In contrast, electrospinning technology can produce continuous fibers with adjustable diameter, thickness, porosity, and roughness, offering the advantage of tuning superhydrophobicity and transparency at the micro- and nanoscale. However, superhydrophobic coatings prepared by electrospinning technology have the following drawbacks: 1. Transparency loss due to reflection / refraction at the air-fiber interface; 2. Poor adhesion between the glass substrate and the coating. To avoid transparency loss due to reflection / refraction at the air-fiber interface, the composition and pore morphology of the nanofiber membrane must be precisely controlled. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing and applying a transparent superhydrophobic coating, which can improve at least one of the following problems: reducing transparency loss and improving the adhesion between the coating and the substrate.

[0007] As mentioned above, in a first aspect, the present invention provides a method for preparing a transparent superhydrophobic coating, comprising the following steps:

[0008] A spinning solution was prepared by blending polyvinylidene fluoride-trifluoroethylene copolymer, PDMS and solvent, and then a superhydrophobic transparent coating was formed on the substrate surface by electrospinning.

[0009] According to an embodiment of the present invention, the mass ratio of the polyvinylidene fluoride-trifluoroethylene copolymer to PDMS is 1:0 to 1:10, preferably the mass ratio of the polyvinylidene fluoride-trifluoroethylene copolymer to PDMS is 1:0 to 1:6, for example 1:0, 1:1, 1:2, 1:3, 1:4.

[0010] According to an embodiment of the present invention, the concentration of polyvinylidene fluoride-trifluoroethylene copolymer and PDMS in the spinning solution is 5 to 30 wt%, preferably 10 to 20 wt%, for example 15 wt%.

[0011] According to an embodiment of the present invention, the solvent is selected from one or more of methanol, ethanol, acetone, DMF, THF, and n-hexane, for example, DMF or a mixed solution of DMF and THF.

[0012] According to an embodiment of the present invention, the process of blending polyvinylidene fluoride-trifluoroethylene copolymer, PDMS and solvent to obtain a spinning solution includes the following steps: adding polyvinylidene fluoride-trifluoroethylene copolymer and PDMS to DMF solution and mixing until dissolved to obtain a spinning solution.

[0013] According to an embodiment of the present invention, the mass ratio of the polyvinylidene fluoride-trifluoroethylene copolymer to PDMS and solvent is 1:(1-6), preferably 1:(1-4), for example 1:1.

[0014] According to an embodiment of the present invention, the mixing is carried out at a temperature of room temperature to 80°C, preferably at a temperature of 50 to 70°C, for example, 60°C.

[0015] According to an embodiment of the present invention, the mixing time is 1 to 8 hours, preferably 2 to 6 hours, for example 3 hours.

[0016] According to an embodiment of the present invention, the mixing is carried out under stirring conditions.

[0017] According to an embodiment of the present invention, the process of blending polyvinylidene fluoride-trifluoroethylene copolymer and PDMS to obtain a spinning solution specifically includes the following steps: first, mixing PDMS with a curing agent to obtain a PDMS prepolymer, and then adding the PDMS prepolymer and polyvinylidene fluoride-trifluoroethylene copolymer to a mixed solution of DMF and THF, and mixing until dissolved.

[0018] According to an embodiment of the present invention, before forming a superhydrophobic transparent coating on the substrate surface by electrospinning, the following step is further included: cleaning the substrate surface.

[0019] According to an embodiment of the present invention, cleaning the substrate surface includes the following steps: ultrasonically cleaning the substrate with isopropanol, acetone and deionized water and then drying it.

[0020] According to an embodiment of the present invention, the drying is carried out at a temperature of 30 to 100°C, for example, 60°C.

[0021] According to an embodiment of the present invention, the drying time is 10 to 60 minutes, for example, 30 minutes.

[0022] According to an embodiment of the present invention, after cleaning the substrate surface and before forming a superhydrophobic transparent coating on the substrate surface by electrospinning, the method further includes the following step: coating the substrate surface with a crosslinking agent to form a crosslinking agent layer, wherein the crosslinking agent layer is used to crosslink with polyvinylidene fluoride-trifluoroethylene copolymer and PDMS to form a transparent superhydrophobic coating.

[0023] According to an embodiment of the present invention, the crosslinking agent is selected from one or more of trimethylchlorosilane, triethoxysilane, methyltriethoxysilane, trimethoxysilane, and methyltrimethoxysilane, for example, trimethylchlorosilane.

[0024] According to an embodiment of the present invention, coating the substrate surface with a crosslinking agent includes the following steps: dissolving the crosslinking agent in a solvent to form a crosslinking agent solution, and coating the crosslinking agent solution onto the substrate surface.

[0025] According to an embodiment of the present invention, the concentration of the crosslinking agent solution is 0.1 to 0.5 wt%, for example, 0.2 wt%.

[0026] As an example, the crosslinking agent solution is a 0.2 wt% trimethylchlorosilane-hexane solution.

[0027] According to an embodiment of the present invention, the substrate is selected from glass, metal, cloth, filter paper, etc., for example, glass.

[0028] According to an embodiment of the present invention, after the crosslinking agent layer is formed on the substrate surface and before the superhydrophobic transparent coating is formed on the substrate surface by electrospinning, the following step is further included: coating the surface of the crosslinking agent layer with a promoting group to form a promoting agent layer.

[0029] According to an embodiment of the present invention, coating an accelerator on the surface of a crosslinking agent layer includes the following steps: mixing PDMS prepolymer with a curing agent, coating the mixture on the surface of the crosslinking agent layer, and curing it under a UV lamp to form an accelerator layer.

[0030] According to an embodiment of the present invention, the mass ratio of the PDMS prepolymer to the curing agent is (5-20):1, preferably (10-15):1, for example, 10:1.

[0031] According to an embodiment of the present invention, the curing agent is selected from at least one of platinum-catalyzed addition curing agents, hydrogen-containing silicone oil, methoxysilane, ethoxysilane, dipropylbenzene peroxide, benzyl peroxide, tert-butyl peroxide, etc., for example, a platinum-catalyzed addition curing agent.

[0032] According to an embodiment of the present invention, the electrospinning is carried out at a constant flow rate of 0.1 to 3 mL / h at a voltage of 11 to 20 kV, for example at a constant flow rate of 0.5 mL / h at a voltage of 14.5 kV.

[0033] According to an embodiment of the present invention, after electrospinning, the method further includes the following step: drying the substrate after electrospinning.

[0034] According to an embodiment of the present invention, the drying is carried out at a temperature of 30 to 100°C, for example, 60°C.

[0035] According to an embodiment of the present invention, the drying time is 2 to 6 hours, for example, 4 hours.

[0036] According to an embodiment of the present invention, the initial contact angle of the transparent superhydrophobic coating is 154.6° and the roll-off angle is approximately 9°.

[0037] According to an embodiment of the present invention, the transparent superhydrophobic coating has a slip angle of approximately 20° after continuous water spraying for 45 minutes.

[0038] According to an embodiment of the present invention, the transparent superhydrophobic coating has a transmittance of >80% for light in the range of 400–1200 nm, preferably >85%, and more preferably ≥90%.

[0039] Secondly, the present invention provides an application of a transparent superhydrophobic coating prepared by the method described above in glass waterproofing.

[0040] Beneficial effects

[0041] 1) This invention increases light transmittance by introducing high-transmittance PDMS material onto the substrate, resulting in a light-transmitting coating with a light transmittance of >85% in the range of 400-1200nm. At the same time, the light-transmitting coating not only has good scratch resistance but also good hydrophobic properties: the initial contact angle is 154.6°, the roll-off angle is about 9°, and it still maintains hydrophobicity after continuous water spraying for 45 minutes. The water contact angle (WCA) decreases slightly, and the slip angle (SA) increases slightly to about 20°.

[0042] 2) This invention pre-forms an accelerator layer and a crosslinking agent layer on a substrate. The crosslinking agent layer increases the connection strength between the accelerator layer and the substrate, allowing the crosslinking agent layer and the substrate to be connected not only by hydrogen bonds but also by chemical bonds. The crosslinking agent layer is used to crosslink with polyvinylidene fluoride-trifluoroethylene copolymer and PDMS in the electrospinning solution, so that the fibers formed by electrospinning adhere tightly to the substrate. The superhydrophobic coating formed by electrospinning has a crosslinked nanofiber structure, and the fibers crosslink to form a network structure with a large number of pores, thereby forming a superhydrophobic coating with both superhydrophobicity and optical transparency. Attached Figure Description

[0043] Figure 1 The schematic diagram and flowchart illustrate the principle of preparing the transparent superhydrophobic coating according to this invention;

[0044] Figure 2 The scanning electron microscope image and fiber size distribution diagram of the electrospun coating prepared in Example 1 of the present invention are shown.

[0045] Figure 3 This is a comparison diagram of the light transmittance of the electrospun coatings prepared under different conditions in Example 1 of the present invention;

[0046] Figure 4 This is a pencil abrasion resistance test of the electrospun coating prepared under the condition of G being 1:3 in Example 1 of the present invention;

[0047] Figure 5 Water flow impact resistance test of the superhydrophobic electrospun coating prepared under the condition of G being 1:3 in Example 1 of the present invention;

[0048] Figure 6 The images shown are physical photos and scanning electron microscope images of the superhydrophobic electrospun coating prepared under the condition of G being 1:1 in Example 2 of this invention.

[0049] Figure 7 The images shown are physical images and scanning electron microscope images of the superhydrophobic electrospinning coating prepared under the condition of G being 1:4 in Example 2 of this invention. Detailed Implementation

[0050] The superhydrophobic coating, its preparation method, and its application of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0051] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0052] Example 1

[0053] A method for preparing a transparent superhydrophobic coating includes the following steps:

[0054] First, the glass slide was ultrasonically cleaned with isopropanol, acetone, and deionized water, and then dried in an oven at 60°C for 30 minutes. A 0.2 wt% MTS (methyltrichlorosilane) solution (using n-hexane as solvent) was prepared by magnetic stirring and coated onto the surface of the glass slide with a brush. After drying at 60°C for 15 minutes, a crosslinking agent layer was obtained. A accelerator solution was formed by mixing PDMS (polydimethylsiloxane) prepolymer and a curing agent (platinum-catalyzed addition curing agent, from Sylgard 184B) at a weight ratio of 10:1 and stirring at 1000 rpm for 15 minutes at room temperature to make it homogeneous. The accelerator solution was coated onto the crosslinking agent layer and cured under ultraviolet light to achieve a strong bond, forming an accelerator layer film, thus obtaining the pretreated glass slide.

[0055] To electrospin the PVDF-TrFE (polyvinylidene fluoride-trifluoroethylene) / PDMS copolymer (PVDF-TrFE to PDMS mass ratio from 1:0 to 1:4, i.e., G-1:0 / 1:1 / 1:2 / 1:3 / 1:4) nanofibers, the PVDF-TrFE / PDMS copolymer was dissolved in a DMF solution at a mass ratio of 1:1 to form a 15wt% electrospinning solution. The solution was stirred at 60°C for 3 hours and then electrospinned onto pre-treated glass slides at a constant flow rate of 0.5 mL / h at 14.5 kV. The electrospinning process parameters were optimized by adjusting the time to achieve the desired thickness and water contact angle. The coated glass slides were then dried at 60°C for 4 hours to remove residual solvent.

[0056] See Figure 1The diagram shown is a schematic diagram and process flow diagram of electrospinning in this embodiment. In order to improve the robustness of transparent superhydrophobic electrospun (TESH) nanofibers, the present invention first performs a pretreatment step of MTS silanization (TMS-s) on glass, then deposits PDMS prepolymer to form a promoting layer, and then coats PVDF-TrFE / PDMS nanofibers on the promoting layer by electrospinning to form a transparent superhydrophobic coating, thereby obtaining a glass sheet with a superhydrophobic coating.

[0057] See Figure 2 The image shown is a scanning electron microscope image of the electrospun coating prepared in this embodiment. As can be seen from the image, the coating has a cross-linked nanofiber structure, and the fibers cross-link to form a network structure. The average diameter of the fibers is 101.78±3nm.

[0058] See Figure 3 As shown in the figure, the transmittance comparison diagram of the electrospun coating prepared under different conditions in this embodiment shows that when the mass ratio of PVDF-TrFE to PDMS is 1:3, the transmittance is optimal, with a transmittance ≥90% under light irradiation in the wavelength range of 400nm to 1200nm; and when the mass ratio of PVDF-TrFE to PDMS is in the range of 1:1 to 1:4, the transmittance is ≥80% under light irradiation in the wavelength range of 400nm to 1200nm. That is, the electrospun coating prepared by this invention has good transmittance.

[0059] See Figure 4 As shown, the wear resistance test of the superhydrophobic coating prepared by G-1:3 in this embodiment was carried out according to ASTM D3363 standard. The mechanical strength of the superhydrophobic coating was verified by pencil hardness test, showing that it has scratch resistance when the pencil hardness reaches 4H; however, when a pencil with a hardness greater than 6H is used, scratches appear on the surface. The test shows that the superhydrophobic coating prepared by G-1:3 has a significant hardness of 4H and has good scratch resistance according to ASTM D3363 standard.

[0060] See Figure 5 As shown, the superhydrophobic coating prepared under the condition of G being 1:3 in this embodiment is subjected to water flow impact test. The test results show that the initial contact angle of the superhydrophobic coating is 154.6°, the roll-off angle is about 9°, and it still maintains hydrophobicity after continuous water spraying for 45 minutes. The water contact angle (WCA) decreases slightly, and the slip angle (SA) increases slightly to about 20°, indicating that it has good hydrophobicity.

[0061] Example 2

[0062] A method for preparing a transparent superhydrophobic coating includes the following steps:

[0063] First, the glass slide was ultrasonically cleaned with isopropanol, acetone, and deionized water, and then dried in an oven at 60°C for 30 minutes. A 0.5 wt% MTS (methyltrichlorosilane) solution (using n-hexane as solvent) was prepared by magnetic stirring and coated onto the surface of the glass slide with a brush. After drying at 60°C for 15 minutes, a crosslinking agent layer was obtained. A accelerator solution was formed by mixing PDMS (polydimethylsiloxane) prepolymer and a curing agent (platinum-catalyzed addition curing agent) at a weight ratio of 20:1 and stirring at 1000 rpm for 15 minutes at room temperature until homogeneous. This accelerator solution was then coated onto the crosslinking agent layer and cured under ultraviolet light to achieve a strong bond, forming an accelerator film, thus obtaining the pretreated glass slide.

[0064] To electrospin the PVDF-TrFE (polyvinylidene fluoride-trifluoroethylene) / PDMS copolymer (PVDF-TrFE to PDMS mass ratio from 1:0 to 1:4, i.e., G-1:0 / 1:1 / 1:2 / 1:3 / 1:4) nanofibers, the PVDF-TrFE / PDMS copolymer was dissolved in a 1:1 mass ratio of DMF:THF (1:1) to form a 10wt% electrospinning solution. The solution was stirred at room temperature for 8 hours and then electrospinned onto a pre-treated glass slide at a constant flow rate of 3 mL / h at 11 kV. The electrospinning process parameters were optimized by adjusting the time to achieve the desired thickness and water contact angle. The coated glass slide was then dried at 60°C for 4 hours to remove residual solvent, resulting in a glass slide with a superhydrophobic coating.

[0065] See Figure 6 As shown, the superhydrophobic coating prepared in this embodiment has a cross-linked nanofiber structure, and the fibers cross-link to form a network structure, and has good light transmittance. After testing, the light transmittance is >81.5%.

[0066] Example 3

[0067] A method for preparing a transparent superhydrophobic coating includes the following steps:

[0068] First, the glass slide was ultrasonically cleaned with isopropanol, acetone, and deionized water, and then dried in an oven at 60°C for 30 minutes. A 0.1 wt% MTS (methyltrichlorosilane) solution (using n-hexane as solvent) was prepared by magnetic stirring and coated onto the surface of the glass slide with a brush. After drying at 60°C for 60 minutes, a crosslinking agent layer was obtained. A accelerator solution was formed by mixing PDMS (polydimethylsiloxane) prepolymer and a curing agent (platinum-catalyzed addition curing agent) at a weight ratio of 10:1 and stirring at 1000 rpm for 30 minutes at room temperature until homogeneous. This accelerator solution was then coated onto the crosslinking agent layer and cured under ultraviolet light to achieve a strong bond, forming an accelerator layer film, thus obtaining the pretreated glass slide.

[0069] To electrospin the PVDF-TrFE (polyvinylidene fluoride-trifluoroethylene) / PDMS copolymer (PVDF-TrFE to PDMS mass ratio from 1:0 to 1:4, i.e., G-1:0 / 1:1 / 1:2 / 1:3 / 1:4) nanofibers, the PVDF-TrFE / PDMS copolymer was dissolved in a 1:1 mass ratio of DMF:THF (1:1) to form a 20wt% electrospinning solution. The solution was stirred at 60°C for 3 hours and then electrospinned onto a pre-treated glass slide at a constant flow rate of 0.1 mL / h at 20 kV. The electrospinning process parameters were optimized by adjusting the time to achieve the desired thickness and water contact angle. The coated glass slide was then dried at 60°C for 4 hours to remove residual solvent, resulting in a glass slide with a superhydrophobic coating.

[0070] See Figure 7 As shown, the superhydrophobic coating prepared in this embodiment has a cross-linked nanofiber structure, and the fibers cross-link to form a network structure, which has good hydrophobicity and good light transmittance. After testing, the light transmittance is >80%.

[0071] The specific embodiments of the present invention have been described above by way of example. However, the scope of protection of the present invention is not limited to the above exemplary embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a transparent superhydrophobic coating, characterized in that, The preparation method includes the following steps: A spinning solution is prepared by blending polyvinylidene fluoride-trifluoroethylene copolymer, PDMS, and a solvent. A superhydrophobic transparent coating is then formed on the substrate surface using electrospinning. The mass ratio of the polyvinylidene fluoride-trifluoroethylene copolymer to PDMS is 1:1 to 1:10, and the concentrations of the polyvinylidene fluoride-trifluoroethylene copolymer and PDMS in the spinning solution are 5 to 30 wt%. Before forming a superhydrophobic transparent coating on the substrate surface using electrospinning, the following steps are also included: cleaning the substrate surface, coating the substrate surface with a crosslinking agent to form a crosslinking agent layer, coating the surface of the crosslinking agent layer with an accelerator to form an accelerator layer, wherein the crosslinking agent layer is used to crosslink with polyvinylidene fluoride-trifluoroethylene copolymer and PDMS to form a transparent superhydrophobic coating; The crosslinking agent is selected from one or more of triethoxysilane, methyltriethoxysilane, trimethoxysilane, and methyltrimethoxysilane; Coating the substrate surface with a crosslinking agent includes the following steps: dissolving the crosslinking agent in a solvent to form a crosslinking agent solution, and coating the crosslinking agent solution onto the substrate surface, wherein the concentration of the crosslinking agent solution is 0.1~0.5wt%; The process of coating an accelerator onto the surface of a crosslinking agent layer includes the following steps: mixing a PDMS prepolymer with a curing agent and coating the mixture onto the surface of the crosslinking agent layer, then curing it under a UV lamp to form an accelerator layer. The mass ratio of the PDMS prepolymer to the curing agent is (5~20):1, and the curing agent is selected from platinum-catalyzed addition curing agents.

2. The method for preparing the transparent superhydrophobic coating according to claim 1, characterized in that, The solvent is selected from one or more of methanol, ethanol, acetone, DMF, THF, and n-hexane.

3. The method for preparing the transparent superhydrophobic coating according to claim 1, characterized in that, The process of blending polyvinylidene fluoride-trifluoroethylene copolymer, PDMS and solvent to obtain a spinning solution includes the following steps: adding polyvinylidene fluoride-trifluoroethylene copolymer and PDMS to DMF solution and mixing until dissolved to obtain a spinning solution. The mixing is carried out at a temperature of room temperature to 80°C for a time of 1 to 8 hours.

4. The method for preparing the transparent superhydrophobic coating according to any one of claims 1-3, characterized in that, The electrospinning was carried out under constant flow rate of 0.1-3 mL / h at a voltage of 11-20 kV.

5. The method for preparing the transparent superhydrophobic coating according to any one of claims 1-3, characterized in that, After electrospinning, the following step is also included: drying the substrate after electrospinning.

6. The application of a transparent superhydrophobic coating prepared by the method of any one of claims 1-5 in glass waterproofing.

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